Control for a conveyor take-up

ABSTRACT

Relative movement between the fixed and movable frames of a conveyor take-up is controlled by a hydraulic cylinder and piston unit, the cylinder of which is connected to one of the frames and the piston to the other, the movable take-up frame being normally urged in an extending direction to apply tension to the conveyor chain. The hydraulic cylinder is connected to a fluid passage containing an orifice which permits fluid flow at a controlled rate in response to extending movement of the take-up, and containing a check valve which obstructs fluid flow in the opposite direction and prevents collapsing movement of the takeup. A normally open solenoid valve in this passage is operable to obstruct flow in both directions in the event the conveyor drive shuts down. A pressure relief valve mounted in an alternate passage permits collapsing take-up movement in the event of abnormal tension in the conveyor chain. In one embodiment, the hydraulic cylinder is combined with an air cylinder, and the pistons of both cylinders are mounted on a common rod, the air cylinder being supplied with regulated air pressure to apply a normal extending force to the movable take-up frame.

United States Patent [1 1 Dehne Dec. 11, 1973 CONTROL FOR A CONVEYORTAKE-UP [75] Inventor: Clarence A. Dehne, Farmington ABSTRACT TownshipMich Relative movement between the fixed and movable [73] Assignee:Jervis B. Webb Company, Detroit, frame,s of P is commlled by a b Michdrauhc cylinder and piston unit, the cylinder of which is connected toone of the frames and the piston to the Filedl 1971 other, the movabletake-up frame being normally [21] AppL 203,210 urged in an extendingdirection to apply tension to the conveyor chain. The hydraulic cylinder18 connected to a fluid passage containing an orifice which permits U.S.Cl. flow at a controlled ate in response to extending [51] Int. Cl.movement of the takeq p and containing a check of Search A, valveobstructs flow in the opposite direc- 198/208, 139 tion and preventscollapsing movement of the take-up.

A normally open solenoid valve in this passage is oper- References Citedable to obstruct flow in both directions in the event UNITED STATESPATENTS the conveyor drive shuts down. A pressure relief valve 2,713,9557/1955 Bishop 1981208 mounted in an alternate P 's Permits collapsing2,460,196 [[1949 s 91/411 A take-up movement in the event of abnormaltension in 2,532,663 12/1950 Ellis 91/436 the conveyor chain. In oneembodiment, the hydraulic 3,452,645 8/1969 Barltrop 91/437 cylinder iscombined with an air cylinder, and the pis- 2,438,0 3/19 Me c e 198/208tons of both cylinders are mounted on a common rod, 2,794,538 6/1957Schenk 198/208 the i cylinder i li d ith regulated air pres- PrimaryExaminer-Richard E. Aegerter Assistant ExaminerJoseph E. ValenzaAttorneyFarley et a].

sure to apply a normal extending force to the movable take-up frame.

6 Claims, 4 Drawing Figures PATENTEDDEC 11 ms SHEET 10F 2 ATTOZ/VZYSPAIENIEDHH; 1 1 1975 SHEET 2 OF 2 F'IG.2

INVENTOR.

CZAEf/VCZ' A DAV/N5 1 CONTROL FOR A CONVEYOR TAKE-UP SUMMARY OF THEINVENTION The present invention relates to a control for a takeupemployed to apply tension to an endless conveyor chain.

Such a take-up is usually installed following adrive unit for theendless chain, and consists of a fixed frame, and a movable framecarried thereby. The movable frame supports or engages the conveyorchain and is normally urged by spring, counterweight or fluid pressuremeans in a direction such as to apply a tension force to the chain andextend the take-up, thereby compensating for any slack chain which mayresult from chain loading, chain wear, temperature changes, or anycombination of these factors.

ln'many conveyor installations, forces may be created in the conveyorchain, either occasionally or periodically, which tend to collapse atake-up and cause slack chain to appear at some other place in thesystem. An example of a condition that can produce these collapsingforces on the take-up is found in a system where heavily loaded carriersperiodically negoiate a vertical decline located relatively close to atake-up unit; or, in a system where the conveyor chain is driven bymultiple drives, and one drive may occasionally create a collapsingforce on a take-up in an effort to help another drive.

One prior solution to the problem of providing proper take-up operationunder such conditions has merely involved applying to the movabletake-up frame an extending force greater than any collapsing force towhich the take-up is subjected. This creates high tension in theconveyor chain at all times, whether necessary or not; increases theconveyor chain pull requirements considerably, thereby reducing theamount of practical work that can be accomplished; and subjectscomponents of the system to excessive wear and fatigue. A second priorapproach involves the use of a one-way ratchet device which permits thetake-up to extend under the normal tension force but prohibits thetake-up from collapsing. However, should a jam occur in the system andcause an abnormal amount of slack chain to develop, the take-up willextend and lockin place. When normal operating conditions are restored,the chain will remain in a high tension condition because the take-upcannot return. Some conveyor systems include an oven through which thechain passes, and the ratchet device is not satisfactory in this type ofsystem because the take-up must be free to collapse to allow forcontraction of the chain when the system is shut down and the chaintemperature decreases.

The present invention provides a take-up control which automaticallyregulates the operation of the take-up under all conditions such asmentioned above, both normal and abnormal for a particular system, thecontrol acting to prevent undesired collapsing of a take-up under normalconditions, to permit collapsing of the take-up under abnormalconditions, and to allow a return to normal operation when theabnormality has been corrected.

A take-up control constructed in accordance with the invention comprisesa hydraulic unit having a cylinder member and a piston member dividingthe cylinder member into two chambers. One of the cylinder and pistonmembers is connected to the fixed frame of a take-up and the other ofsaid members is connected to the movable frame thereof. A hydrauliccircuit connected to at least one chamber of the hydraulic unit ineludesflow control means for permitting fluid flow in one direction, andobstructing fluid flow in the opposite direction. The direction in whichfluid flow is permitted allows relative movement between the cylinderand piston members occasioned by movement of the movable take-up framein the extending direction.

Preferably, the flow control means includes an orifice which limits therate of fluid flow in the one direction, thereby limitingthe rate ofmovement of the movable take-up frame in the extending direction, and acheck valve connected in series with the orifice to obstruct fluid flowin the opposite direction.

Other preferred components of the hydraulic circuit include a solenoidvalve in series with the orifice and check valve, which solenoid valveis closed in response to a non-driving condition of the conveyor drivingunit; a relief valve in parallel with the orifice and check valve topermit collapsing movement of the movable take-up frame in response toexcessive chain forces in the collapsing direction; a manually operablevalve, in parallel with the orifice and check valve and with the reliefvalve, which when opened provides a free fluid passage; and, a reservoirfor maintaining the chambers and hydraulic circuit full of fluid.

Other features and advantages of the invention will appear from thedescription to follow of the representative embodiments thereofdisclosed in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional elevation of arepresentative take-up construction equipped with the control of theinvention, and including a schematic diagram of the hydraulic circuit ofthe control;

FIG. 2 is a plan view on a reduced scale of the takeup and control shownin FIG. 1;

FIG. 3 is a schematic diagram of a conveyor system incorporating atake-up and the control of the invention; and,

FIG. 4 is a schematic diagram of an alternate form of take-up control.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 3, theconveyor system shown therein includes an endless chain 10, representedby the broken line, driven in the direction indicated by the arrow 12 bya drive unit 13 which includes a drive motor 14 and drive motor controlpanel 15. A take-up 16 is installed downstream in the direction of chaintravel 12 from the drive unit 13 and includes a fixed frame 18 and amovable frame 20 carried thereby, the movable frame engaging the chain10, or supporting the chain 10 through a track on which trolleysconnected to the chain travel, as in a conventional overhead conveyor.Suitable means such as a spring 22 applies a force indicated by thearrows 23 to the movable frame. This force causes the movable frame toapply tension to the conveyor chain 10 and to move in what will bereferred to as an extending direction in the event slack chain shoulddevelop.

An element in the system of FIG. 3 which can produce a force on thetake-up l6 opposite in direction to the force 23 is schematicallydepicted by the box 24. This element could comprise a vertical declinein the conveyor, or a second drive unit for the chain 10, or an oven. Inthe case of a vertical decline, a heavily loaded carrier traversing thisdecline would produce a force on the chain tending to displace themovable take-up frame in an opposite, or what will be referred to as acollapsing, direction. If the element 24 is another drive unit operatingmomentarily faster than the drive unit 13, a similar force will becreated tending to collapse the take-up. If the element 24 is an oventhrough which the chain 10 passes, a collapsing force will be producedwhen the oven is shut off and the chain cools.

Basic conventional structural components of the take-up 16 areillustrated in FIGS. 1 and 2 for a conveyor system in which the chain 10is supported by trolleys 26 from an overhead rail 27. For the fixedframe 18, these components include a pair of side members 30, eachhaving atrack surface 31, and a pair of end members 32 and 33, the endmember 32 being connected to terminal portions 28 of the track 27 forthe trolleys 26. The movable. frame 20 includes a pair of side members34, each having a pair of wheels carried by the track surfaces 31 of thefixed frame, the side members 34 being connected together by end members37 and 38, and these end members being also connected by a centrallongitudinal member 39. A U- shaped track section 40 for the conveyortrolleys 26 is carried by the movable frame, with suitable expansionjoints 42 extending between this U-shaped track section and the terminalportions 28 of the fixed track 27.

The control of the invention comprises a hydraulic unit 44 mounted onthe central longitudinal member 39 of the movable take-up frame, andhaving a cylinder member 45 and a piston member 46. In the constructionshown in FIGS. 1 and 2, the hydraulic unit 44 is combined with an airpressue unit 48 having a cylinder 49 connected in end-to-end relationwith the cylinder 45, and a piston 50. The piston 50 of the air pressureunit 48 and piston 46 of the hydraulic unit 44 are mounted on a commonrod 52 extending axially through the cylinders 45 and 49, and having afree end 53 connected to a bracket 54 attached to the fixed frame endmember 33.

Air pressure is supplied through a line 56 and a regulator 57 connectedtherein, to the cylinder 49 of the air pressure unit 48, and, since theposition of the piston 50 is fixed, this air pressure exerts a forcenormally urging the movable frame 20 in the extending direction. Hence,the air pressure unit 48 performs a function similar to the spring 22 inFIG. 3. It will be understood that in a case where a spring or acounterweight is employed as a means normally urging the movable framein an extending direction, the air pressure unit 48 would not beemployed, and the construction would only include a hydraulic unit 44.Further, although the hydraulic unit 44 is shown with the cylindermember 45 thereof connected to the movable frame 20 and the pistonmember 46 connected to the fixed frame 18, the mounting of the cylinderand piston members can obviously be transposed.

The piston member 46 of the hydraulic unit 44 divides the cylindermember 45 thereof into two chambers 58 and 59 which are connected by ahydraulic circuit 60, as shown in FIG. 1. This circuit 60 includes flowcontrol means, in the form of an orifice 62 and check valve 63 arrangedin series with the orifice in a passageway 64, for permitting fluid flowbetween the chambers 58 and 59 in one direction indicated by the arrow66 and obstructing fluid flow in the opposite direction indicated by thearrow 67. Fluid flow in the direction 66 enables fluid to be displacedfrom the chamber 58 to the chamber 59 as a result of the relativemovement between the cylinder member 45 and piston member 46 which isoccasioned by movement of the movable take-up frame 20 in the extendingdirection, with the rate of flow being controlled by the orifice 62.Fluid flow in the opposite direction 67 is blocked by the check valve 63which prevents relative movement between the cylinder member 45 andpiston member 46 occasioned by movement of the movable take-up frame 20in the collapsing direction.

A normally open solenoid controlled valve 70 is connected in'the passage64 in series with the orifice 62 and check valve 63. This valve 70 isconnected by an electrical interlock 71 to the control panel 15 for theconveyor drive motor 14 so that the valve 70 is closed in response to anon-driving condition of the conveyor driving unit 13.

Connected in a passage 72, in parallel with the passage 64, is apressure relief valve 74 which permits fluid flow to the chamber 58 inthe event fluid pressure in the chamber 59 exceeds the setting of thevalve 74.

A manual valve 76 is installed in a third parallel passage 77. Thisvalve 76 is normally closed, but when opened, fluid is free to flowbetween the chambers 58 and 59 in either direction.

The hydraulic circuit 60 is provided with a reservoir 78 to maintain thechambers 58 and 59, and the components of the circuit 60 filled withhydraulic fluid. Preferably, the reservoir 78 is a combination air-oilunit supplied with air pressure through a line 79 which includes aregulator 80 and a shut-off valve 82 which closes in the event the airpressure fails. A bleeder valve 84 is provided to aid in obtaining andmaintaining a full fluid condition in the hydraulic unit and circuit.Compensation for hydraulic fluid leakage is the only function performedby the reservoir 78 in the construction illustrated because theend-to-end arrangement of the units 44 and 48 results in balancedvolumes of the chambers 58 and 59 of the hydraulic unit. When thehydraulic unit is used separately, as mentioned above, the volumes ofthe chambers 58 and 59 will not be balanced because of the absence ofthe rod 52 in one of the chambers, and the reservoir 78 must havesufficient capacity to compensate for the difference in volume.

In normal operation, a regulated extending force is applied to themovable take-up frame 20 by the air pressure unit 48. As slack chain isdeveloped in the system, the movable frame 20 of the take-up graduallyextends to compensate therefor. The hydraulic unit 44 has no influenceupon this normal take-up action, and does not introduce any additionalchain tension into the system under normal conditions. As the movableframe 20 of the take-up extends, fluid flows from the chamber 58 to thechamber 59 of the hydraulic unit through the normally open valve 70 andorifice 62.

A pressure setting for the relief valve 74 is established at a valuegreater than the pressure created within the chamber 59 as a result of acollapsing force on the take-up occasioned by a normal operatingcondition such as the passage of a carrier through a vertical decline orthe normal balancing action of multiple drives. Hence, when such normalcollapsing forces are imposed upon the movable frame of the take-up, nocollapsing movement thereof ensues due to the action of the check valve63. An abnormal collapsing force, however, will cause the valve 74 toopen and permit corresponding movement of the take-up frame 20.

In the event a jam occurs in the system, creating tension in theconveyor chain which would create an abnormal amount of slack, thecontrol of the invention limits movement of the movable take-up frame 20resulting from this slack. The rate of take-up movement in the extendingdirection, resulting in fluid flow in the direction of the arrow 66 inthe illustrated construction, is limited by the orifice 62. If the jamis severe enough to cause the conveyor drive motor to shut down, thesolenoid valve 70 automatically closes, thereby blocking fluid flowthrough the passage 64 and preventing take-up movement in the extendngdirection.

FIG. 4 illustrates an alternate, all hydraulic form of take-up control.A cylinder 86, connected to the fixed frame 87 of a take-up, has apiston 88 dividing the cylinder into two chambers 89 and 90 and a rod 92suitably connected to the movable take-up frame. A hydraulic circuit 94,containing components similar to those previously described andidentified by the same reference numerals, is connected to one of thechambers 90, and by a line 95to an accumulator 96. Air pressure isapplied through a line 97 to one side of the accumulator diaphram 98.

Flow control means in line 95 of the hydraulic circuit 94 includes anorifice 62 for permitting fluid flow from the accumulator 96 to thechamber 90 and applying a force to the piston 88 to normally urge themovable take-Up frame in the extending direction,as indicated by thearrow 99. Line 95 of the hydraulic circuit 94 also includes a checkvalve 63 to prevent fluid flow and hence movement of the movable take-upframe in the opposite, or collapsing direction. A normally open solenoidcontrolled valve 70 interlocked by a connection 71 to the conveyordriving unit, as previously described, obstructs fluid flow in responseto a nondriving condition of the conveyor driving unit.

As in the previously described embodiment, the hydraulic circuit 94includes a pressure relief valve 74 installed in a by-pass line 100 anda manually operable valve 76 installed in a second by-pass line 101.

In order for the control of the invention to function properly, highcollapsing forces on the movable takeup frame 20 must not be continuous.There must be brief periods when high collapsing forces are not presentin order to permit the normal extending movement of the take-up tocompensate for slack chain.

1 claim:

l. A control for a take-up of a conveyor having an endless chain drivenby a driving unit, the take-up including a fixed frame, a moveable framecarried thereby and supporting the endless chain, and means normallyurging the moveable frame in an extending direction such as to applytension to the endless chain, wherein the improvement comprises:

means for regulating the movement of the moveable frame including, i

a hydraulic unit having a cylinder member and a piston member dividingthe cylinder member into two chambers, one of the cylinder and pistonmembers being connected to the fixed frame of the takeup and the otherof said members being connected to and moveable with the moveable frameof the takefluid flow passages communicating with each of said chambers,

and flow control means connected to at least one of said passages forpermitting fluid flow therethrough at a controlled rate in one directionand a normally open valve for obstructing such fluid flow in said onedirection in response to a non-driving condition of the conveyor drivingunit, said one direction of fluid flow allowing relative movementbetween the cylinder and piston members occasioned by normally urgedmovement of the moveable take-up frame in the extending direction.

2. A control according to claim 1 wherein the flow control meansincludes an orifice and a check valve in series, said normally openvalve is in series with said orifice and check valve, said normally openvalve being electrically interlocked with the conveyor driving unit.

3. A control according to claim 1 wherein said regulating means includesa manually operable valve connected in parallel with the flow controlmeans, said manually operable valve permitting fluid flow in bothdirections when open.

4. A control according to claim 1 wherein said regulating means includesa pressure relief valve connected in parallel with the flow controlmeans, said pressure relief valve being capable of permitting flow inresponse to a hydraulic pressure build-up in excess of a preset valveresulting from force on the moveable takeup frame in the direction ofcollapsing movement thereof.

5. A control according to claim 1 wherein the means normally urging themovable frame in an extending direction includes a hydraulic fluidreser-voir, means for applying pressure to hydraulic fluid containedtherein, said pressure forcing hydraulic fluid through the flow controlmeans in said one direction.

6. A control according to claim 1 wherein the means normally urging themovable frame in an extending direction includes a second fluid pressurecylinder member connected to the cylinder member of said hydraulic unitin end-to-end relation, a rod extending through the cylinder member ofthe hy-draulic unit and into the second fluid pressure cylinder member,a second piston secured to the rod within the second fluid pressurecylinder member, and means for applying fluid pressure to one side ofthe second piston for nor-mally urging the movable frame of the take-upin the extending direce x a:

1. A control for a take-up of a conveyor having an endless chain drivenby a driving unit, the take-up including a fixed frame, a moveable framecarried thereby and supporting the endless chain, and means normallyurging the moveable frame in an extending direction such as to applytension to the endless chain, wherein the improvement comprises: meansfor regulating the movement of the moveable frame including, a hydraulicunit having a cylinder member and a piston member dividing the cylindermember into two chambers, one of the cylinder and piston members beingconnected to the fixed frame of the take-up and the other of saidmembers being connected to and moveable with the moveable frame of thetake-up, fluid flow passages communicating with each of said chambers,and flow control means connected to at least one of said passages forpermitting fluid flow therethrough at a controlled rate in one directionand a normally open valve for obstructing such fluid flow in said onedirection in response to a nondriving condition of the conveyor drivingunit, said one direction of fluid flow allowing relative movementbetween the cylinder and piston members occasioned by normally urgedmovement of the moveable take-up frame in the extending direction.
 2. Acontrol according to claim 1 wherein the flow control means includes anorifice and a check valve in series, said normally open valve is inseries with said orifice and check valve, said normally open valve beingelectrically interlocked with the conveyor driving unit.
 3. A controlaccording to claim 1 wherein said regulating means includes a manuallyoperable valve connected in parallel with the flow control means, saidmanually operable valve permitting fluid flow in both directions whenopen.
 4. A control according to claim 1 wherein said regulating meansincludes a pressure relief valve connected in parallel with the flowcontrol means, said pressure relief valve being capable of permittingflow in response to a hydraulic pressure build-up in excess of a presetvalve resulting from force on the moveable taKe-up frame in thedirection of collapsing movement thereof.
 5. A control according toclaim 1 wherein the means normally urging the movable frame in anextending direction includes a hydraulic fluid reser-voir, means forapplying pressure to hydraulic fluid contained therein, said pressureforcing hydraulic fluid through the flow control means in said onedirection.
 6. A control according to claim 1 wherein the means normallyurging the movable frame in an extending direction includes a secondfluid pressure cylinder member connected to the cylinder member of saidhydraulic unit in end-to-end relation, a rod extending through thecylinder member of the hy-draulic unit and into the second fluidpressure cylinder member, a second piston secured to the rod within thesecond fluid pressure cylinder member, and means for applying fluidpressure to one side of the second piston for nor-mally urging themovable frame of the take-up in the extending direction.